Diversity factor for load

[Akten]

Hi, when doing load calculation, what is a diversity factor that should be used? Lets say a distribution panel feeds several lighting, receptacle, HVAC loads (AHU, condensor, Exhaust fans, heater, pumps, etc) what would be a good diversity factor that can be used in load calculation?

Is there any standard number that EE's usually follow or how do designers determine a good number for diversity factor?

 

[D. Castor]

Ignoring the NEC requirements for a moment - this depends on what type of facility is being served. The old IEEE Grey book used to have recommended diversity factors for different occupancies, but it is out of print, I think. Diversity is not generally assumed when you get down to panelboard load.

For industrial facilities, treatment plants and power plants that had a lot of installed standby pumps, we typically used to take 70% of the connected MCC loads as a maximum. You can also take credit for non-coincident loads (heating and cooling).

A good reference point is that utilities normally assume that the maximum demand will be about 50% of the calculated NEC load and size their transformer accordingly.

 

[ron]

Unfortunately, the NEC doesn't have many diversity factors for most loads. Maybe a little for receptacles, or for multiple electric ovens, but generally, the NEC 220 calcs that we use for our equipment selection and requests to the utility are very conservative and don't employ diversity unless specifically called out in 220.